Recent work has shown that cyclic AMP, and the synthetic double-stranded polynucleotides, Poly A:U, and Poly I:C influence the immune response. In vitro cellular systems using these compounds have demonstrated a dose dependent effect upon antibody formation with low dosages producing stimulation and large doses causing inhibition. We propose to use guinea pigs to determine the effect of Poly I:C on delayed hypersensitivity (cell mediated immunity) in the intact animals. Dose relationships will be studied using increasing dosages of Poly I:C to test the effect on established delayed hypersensitivity; and later to determine if the induction of the delayed response can be modified by this polynucleotide. Correlates of delayed hypersensitivity are to be assayed in vivo by skin testing; and in vitro, by macrophage migration as a test of migration inhibitory factor (MIF) production.